1. Field of the Invention
This invention relates in general to wrenches of the type commonly known as "speed wrenches" which provide a ratcheting-type action.
2. Description of the Prior Art
The prior art includes a number of different designs of wrenches which provide a ratchet-type action without the use of any ratchet wheel or dog or other additional moving parts to provide the ratcheting action. Such wrenches are commonly referred to as "speed wrenches" and are typically characterized by jaws respectively having long and short driving surfaces for respectively engaging opposite sides or flats of an associated fastener, such as a hexagonal fastener. Both open-end wrench and adjustable wrench versions of such ratcheting-type speed wrenches have been provided. In operation, when the wrench is rotated in a forward torque applying direction, the driving surfaces will firmly grip the fastener for applying torque to it, while when the wrench is rotated in the reverse direction the driving surfaces will slip or "ratchet" over the fastener surfaces to facilitate movement of the wrench to engagement with a different set of fastener flats without having to lift the wrench from the fastener.
A common prior art speed wrench configuration is designated by the numeral 10 in FIGS. 1 and 2 and includes long and short driving surfaces 11 and 12 interconnected by a generally V-shaped throat which includes flat throat surfaces 13 interconnected by an arcuate corner recess 14. Such recesses 14 may also be provided at the junctions between the throat surfaces 13 and the driving surfaces 11 and 12. The wrench 10 is illustrated as used with a hexagonal fastener 15 having six flats or side surfaces 16 interconnected at six equal-angle corners 17. The wrench 10 is designed so that when an appropriately-sized fastener 15 is disposed between the jaws, the corner recesses 14 will provide clearance for the fastener corners 17. Ideally, if both the wrench 10 and the fastener 15 are accurately sized, the fastener 15 will fit snugly between the wrench jaws and the fastener corners 17 will remain in the corner recesses 14 during a torque applying operation.
Such prior speed wrenches work satisfactorily when the wrench is properly sized for the fastener with which it is being used. However, in practice, fasteners are manufactured to relatively wide tolerances, resulting in considerable variation in the dimensions of fasteners which are nominally of the same size. To a lesser extent, there are also tolerance variations in the spacing between driving surfaces of open-end wrenches of the same nominal size. As a result, there may be considerable clearance or play between the fastener and a wrench which is nominally of the proper size for that fastener. It is not uncommon for this play to be such that it is necessary to rotate the wrench through an angle of as great as 10.degree. before bringing the driving surfaces into firm torque applying engagement with the fastener flats.
When, because of tolerance variations in the parts, the wrench 10 must be rotated through several degrees in order to bring the driving surfaces 11 and 12 into firm torque applying engagement with opposed fastener flats 16, the corner 17 disposed in the wrench throat will ride up out of the corner recess 14 in the throat and onto the adjacent throat surface 13, as can be seen in FIG. 2. This creates a camming action between the throat surface 13 and the fastener corner 16 which tends to urge the fastener 15 outwardly away from the throat. Thus, the short driving surface 12 is slid down closer to the adjacent corner of the fastener and, if this relative rotation between the wrench 10 and the fastener 15 continues far enough, the short driving surface 12 will slip off the fastener. Even if firm gripping action with the fastener is achieved, the short driving surface 12 will be gripping the adjacent fastener flat 16 closer to the corner and will tend to wear or deform the corner more readily, as indicated at 18 in FIG. 2, further exacerbating the tendency to slip during a torque applying operation. The net result is that the ultimate torque which can be applied to the fastener 15 is greatly reduced.